Variational algorithms to remove stationary noise: applications to microscopy imaging

A framework and an algorithm are presented in order to remove stationary noise from images. This algorithm is called variational stationary noise remover. It can be interpreted both as a restoration method in a Bayesian framework and as a cartoon+texture decomposition method. In numerous denoising applications, the white noise assumption fails. For example, structured patterns such as stripes appear in the images. The model described here addresses these cases. Applications are presented with images acquired using different modalities: scanning electron microscope, FIB-nanotomography, and an emerging fluorescence microscopy technique called selective plane illumination microscopy.     

Survey and comparison of message authentication solutions on wireless sensor networks

Security is an important concern in any modern network. This also applies to Wireless Sensor Networks (WSNs), especially those used in applications that monitor sensitive information (e.g., health care applications). However, the highly constrained nature of sensors imposes a difficult challenge: their reduced availability of memory, processing power and energy hinders the deployment of many modern cryptographic algorithms considered secure. For this reason, the choice of the most memory-, processing- and energy-efficient security solutions is of vital importance in WSNs. To date, a number of extensive analyses comparing different encryption algorithms and key management schemes have been developed, while very little attention has been given to message authentication solutions. In this paper, aiming to close this gap, we identify cipher-based Message Authentication Codes (MACs) and Authenticated Encryption with Associated Data (AEAD) schemes suitable for WSNs and then evaluate their features and performance on a real platform (TelosB). As a result of this analysis, we identify the recommended choices depending on the characteristics of the target network and available hardware.     

A design methodology for high-order class-D audio amplifiers

This paper presents a design methodology for high-order class-D amplifiers, based on their similarity with sigma–delta ( $\Upsigma\Updelta$ ) modulators, for which established theory and toolboxes are available. The proposed methodology, which covers the entire design flow, from specifications to component sizing, is validated with three design examples, namely a second-order, a third-order, and a fourth-order class-D amplifier. Moreover, the third-order class-D amplifier has been integrated on silicon and characterized, further confirming the validity of the whole design flow. The achieved results demonstrate that high-order class-D amplifiers can achieve total-harmonic-distortion (THD) performance compatible with the specifications of high-end audio applications (THD  ≈ 90 dB), which would be unfeasible with conventional first-order class-D amplifiers.     

STC power for 15 MW of PV comparing nameplate,initial power and power after 4 years

To date, the majority of quality controls performed at PV plants are based on the measurement of a small sample of individual modules. Consequently, there is very little representative data on the real Standard Test Conditions (STC) power output values for PV generators. This paper presents the power output values for more than 1300 PV generators having a total installed power capacity of almost 15.3 MW. The values were obtained by the INGEPER‐UPNA group, in collaboration with the IES‐UPM, through a study to monitor the power output of a number of PV plants from 2006 to 2009. This work has made it possible to determine, amongst other things, the power dispersion that can be expected amongst generators made by different manufacturers, amongst generators made by the same manufacturer but comprising modules of different nameplate ratings and also amongst generators formed by modules with the same characteristics. The work also analyses the STC power output evolution over time in the course of this 4‐year study. The values presented here could be considered to be representative of generators with fault‐free modules. Copyright © 2012 John Wiley & Sons, Ltd.     

High‐Strength,Durable All‐Silk Fibroin Hydrogels with Versatile Processability toward Multifunctional Applications

Hydrogels are the focus of extensive research due to their potential use in fields including biomedical, pharmaceutical, biosensors, and cosmetics. However, the general weak mechanical properties of hydrogels limit their utility. Here, pristine silk fibroin (SF) hydrogels with excellent mechanical properties are generated via a binary‐solvent‐induced conformation transition (BSICT) strategy. In this method, the conformational transition of SF is regulated by moderate binary solvent diffusion and SF/solvent interactions. β‐sheet formation serves as the physical crosslinks that connect disparate protein chains to form continuous 3D hydrogel networks, avoiding complex chemical and/or physical treatments. The Young's modulus of these new BSICT–SF hydrogels can reach up to 6.5 ± 0.2 MPa, tens to hundreds of times higher than that of conventional hydrogels (0.01–0.1 MPa). These new materials fill the “empty soft materials' space” in the elastic modulus/strain Ashby plot. More remarkably, the BSICT–SF hydrogels can be processed into different constructions through different polymer and/or metal‐based processing techniques, such as molding, laser cutting, and machining. Thus, these new hydrogel systems exhibit potential utility in many biomedical and engineering fields.     

Large‐Area Fabrication of Periodic Arrays of Nanoholes in Metal Films and Their Application in Biosensing and Plasmonic‐Enhanced Photovoltaics

Plasmonics is a fast developing research area with a great potential for practical applications. However, the implementation of plasmonic devices requires low cost methodologies for the fabrication of organized metallic nanostructures that covers a relative large area (～1 cm²). Here the patterning of periodic arrays of nanoholes (PANHs) in gold films by using a combination of interference lithography, metal deposition, and lift off is reported. The setup allows the fabrication of periodic nanostructures with hole diameters ranging from 110 to 1000 nm, for 450 and 1800 nm of periodicity, respectively. The large areas plasmonic substrates consist of 2 cm × 2 cm gold films homogeneously covered by nanoholes and gold films patterned with a regular microarray of 200 μm diameter circular patches of PANHs. The microarray format is used for surface plasmon resonance (SPR) imaging and its potential for applications in multiplex biosensing is demonstrated. The gold films homogeneously covered by nanoholes are useful as electrodes in a thin layer organic photovoltaic. This is first example of a large area plasmonic solar cell with organized nanostructures. The fabrication approach reported here is a good candidate for the industrial‐scale production of metallic substrates for plasmonic applications in photovoltaics and biosensing.     

Reinventing Butyl Rubber for Stretchable Electronics

The development of stretchable electronic devices that are soft and conformable has relied heavily on a single material—polydimethylsiloxane—as the elastomeric substrate. Although polydimethylsiloxane has a number of advantageous characteristics, its high gas permeability is detrimental to stretchable devices that use materials sensitive to oxygen and water vapor, such as organic semiconductors and oxidizable metals. Failing to protect these materials from atmosphere‐induced decomposition leads to premature device failure; therefore, it is imperative to develop elastomers with gas barrier properties that enable stretchable electronics with practical lifetimes. Here, butyl rubber—a material with an intrinsically low gas permeability traditionally used in the innerliners of tires to maintain air pressure—is reinvented for stretchable electronics. This new material is smooth and optically transparent, possesses the low gas permeability typical of butyl rubber, and vastly outperforms polydimethylsiloxane as an encapsulating barrier to prevent the atmospheric degradation of sensitive electronic materials and the premature failure of functioning organic devices. The merits of transparent butyl rubber presented here position this material as an important counterpart to polydimethylsiloxane that will enable future generation stretchable electronics.     

Non-critical saddle-node cycles and robust non-hyperbolic dynamics

We study arcs of diffeomorphisms (f_t) in manifolds of dimension greater than or equal to three bifurcating via non-critical saddle-node cycles. We construct an open set j of such arcs for which, after the bifurcation, every diffeomorphism j does not satisfy Axiom A. We also exhibit an open subset j' of j such that after the bifurcation every diffeomorphism has a partially hyperbolic set of saddle-type which is persistent, locally maximal and transitive. As a consequence, we get a submanifold of codimension-1 of diffeomorphisms with a saddle-node that locally separates the set of Morse-Smale systems from the diffeomorphisms with a partially hyperbolic transitive set.     

Numerical simulation of dam construction using low-CO<Subscript>2</Subscript>-emission concrete

Cement production gives rise to CO₂ emissions generated by the calcination of CaCO₃ and by the combustion of fossil fuels, being responsible for about 5% of the global CO₂ emissions. These emissions can be substantially reduced if cement replacement materials are used. In this paper two residual ashes that can be used as mineral additions are considered: sugar cane bagasse ash and rice husk ash. A case study of the construction of a dam with a blended material composed by cement and these two ashes is presented, indicating the potentiality of its use for civil engineering applications. The analyses were performed using experimental and numerical tools developed on the basis of a thermo-chemo-mechanical model. This model considers the coupling, within the theory of thermodynamics, of the several phenomena that intervene in the hydration process, namely, exothermicity, thermo-activation, chemo-plasticity, evolution of thermal and mechanical properties with the hydration reaction, which includes creep and relaxation.